"Busy Bull, s" joke

A man takes his wife to the stock show. They start heading down the alley that had the bulls. They come up to the first bull and his sign stated: "
This bull mated 50 times last year."
The wife turns to her husband and says, "
He mated 50 times in a year, you could learn from him."
They proceed to the next bull and his sign stated: "
This bull mated 65 times last year."
The wife turns to her husband and says, "
This one mated 65 times last year. That is over 5 times a month. You can learn from this one, also."
They proceeded to the last bull and his sign said: "
This bull mated 365 times last year."
The wife's mouth drops open and says, "
WOW! He mated 365 times last year. That is ONCE A DAY!!! You could really learn from this one."
The man turns to his wife and says, "
Go up and see if it was 365 times with the same cow."